1. Field of the Invention
The present invention relates to mobile communications systems and, more specifically, to a method and system for optimizing performance of a mobile communications system.
2. Background of the Invention
FIG. 1 shows a block diagram of a conventional cellular radiotelephone communication system 5 which includes cells 6, radio base stations or cell sites 8, and a Mobile Telephone Switching Office (MTSO) or mobile telephone switching center 9. As a mobile telephone customer 7 moves from one cell to another a switch in the MTSO automatically switches connections with the respective radio base stations to maintain a continuous connection with the public switched network (not shown). Typically, a switch in an MTSO 9 is connected to approximately one hundred cell sites.
A problem associated with the management of a cellular radiotelephone communications system is geographically locating an area within the zone of radio coverage or cell where faulty coverage exists. An example would be an area within a cellular telephone system that provides poor service due to moderate levels of interference. Typically, this situation is uncovered in one of two ways; customer complaints or the persistent drive team testing by system operators. Neither of these approaches, however, provides a very timely or comprehensive means of identifying, diagnosing, and curing faulty coverage.
In response to these deficiencies, the cellular industry has turned to the aid of electromagnetic coverage prediction tools to assist in the search for holes in the coverage. Typically, these methods of monitoring system performance include observing downlink information along with other system parameters. (Downlink being defined as signals travelling from the cell site to the mobile unit and uplink being defined &as signals travelling from the mobile unit to the cell site). The assumption has been that if the downlink was closed (i.e., a good connection was attained), the available uplink power would be sufficient to close the uplink.
One such electromagnetic coverage tool which takes into account uplink information is discussed by Kurt Nikkinen in “Switch Reality”, AT&T Wireless Service, Apr. 15–16, 1997, and hereby incorporated by reference. This electromagnetic coverage tool involves transmitting location information of a mobile unit to a base station using a cellular modem and also gathering call information from a switch location. The location and call information is then collected at the base station and entered into a map plot.